fuse: handle killpriv in userspace fs
Only userspace filesystem can do the killing of suid/sgid without races.
So introduce an INIT flag and negotiate support for this.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index b7a690e..7cb68b1 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -1703,6 +1703,7 @@
static int fuse_setattr(struct dentry *entry, struct iattr *attr)
{
struct inode *inode = d_inode(entry);
+ struct fuse_conn *fc = get_fuse_conn(inode);
struct file *file = (attr->ia_valid & ATTR_FILE) ? attr->ia_file : NULL;
int ret;
@@ -1710,27 +1711,36 @@
return -EACCES;
if (attr->ia_valid & (ATTR_KILL_SUID | ATTR_KILL_SGID)) {
- int kill;
-
attr->ia_valid &= ~(ATTR_KILL_SUID | ATTR_KILL_SGID |
ATTR_MODE);
- /*
- * ia_mode calculation may have used stale i_mode. Refresh and
- * recalculate.
- */
- ret = fuse_do_getattr(inode, NULL, file);
- if (ret)
- return ret;
- attr->ia_mode = inode->i_mode;
- kill = should_remove_suid(entry);
- if (kill & ATTR_KILL_SUID) {
- attr->ia_valid |= ATTR_MODE;
- attr->ia_mode &= ~S_ISUID;
- }
- if (kill & ATTR_KILL_SGID) {
- attr->ia_valid |= ATTR_MODE;
- attr->ia_mode &= ~S_ISGID;
+ /*
+ * The only sane way to reliably kill suid/sgid is to do it in
+ * the userspace filesystem
+ *
+ * This should be done on write(), truncate() and chown().
+ */
+ if (!fc->handle_killpriv) {
+ int kill;
+
+ /*
+ * ia_mode calculation may have used stale i_mode.
+ * Refresh and recalculate.
+ */
+ ret = fuse_do_getattr(inode, NULL, file);
+ if (ret)
+ return ret;
+
+ attr->ia_mode = inode->i_mode;
+ kill = should_remove_suid(entry);
+ if (kill & ATTR_KILL_SUID) {
+ attr->ia_valid |= ATTR_MODE;
+ attr->ia_mode &= ~S_ISUID;
+ }
+ if (kill & ATTR_KILL_SGID) {
+ attr->ia_valid |= ATTR_MODE;
+ attr->ia_mode &= ~S_ISGID;
+ }
}
}
if (!attr->ia_valid)
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 6db54d0..9940a64 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -547,6 +547,9 @@
/** allow parallel lookups and readdir (default is serialized) */
unsigned parallel_dirops:1;
+ /** handle fs handles killing suid/sgid/cap on write/chown/trunc */
+ unsigned handle_killpriv:1;
+
/*
* The following bitfields are only for optimization purposes
* and hence races in setting them will not cause malfunction
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 1e535f3..b965934 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -910,6 +910,8 @@
fc->writeback_cache = 1;
if (arg->flags & FUSE_PARALLEL_DIROPS)
fc->parallel_dirops = 1;
+ if (arg->flags & FUSE_HANDLE_KILLPRIV)
+ fc->handle_killpriv = 1;
if (arg->time_gran && arg->time_gran <= 1000000000)
fc->sb->s_time_gran = arg->time_gran;
} else {
@@ -941,7 +943,7 @@
FUSE_FLOCK_LOCKS | FUSE_HAS_IOCTL_DIR | FUSE_AUTO_INVAL_DATA |
FUSE_DO_READDIRPLUS | FUSE_READDIRPLUS_AUTO | FUSE_ASYNC_DIO |
FUSE_WRITEBACK_CACHE | FUSE_NO_OPEN_SUPPORT |
- FUSE_PARALLEL_DIROPS;
+ FUSE_PARALLEL_DIROPS | FUSE_HANDLE_KILLPRIV;
req->in.h.opcode = FUSE_INIT;
req->in.numargs = 1;
req->in.args[0].size = sizeof(*arg);